131541: Her period was longer than usual on several occasions. What should she do with regard to fasting?

In my first year of menstruating, my period would last for 6 or 7 days, but in the second year it began to last for approximately nine days. At the end of the second year and in the third year, it began to last between two and three weeks. In Ramadan it lasted 18 days, starting three days before Ramadan, and lasting for 15 days of Ramadan. What is the ruling on that with regard to making up missed fasts?.

Praise be to Allaah.

The scholars differed concerning the maximum length of
menses. The correct view is that there is no minimum or maximum length of
menses, and that a woman’s period may become longer or shorter. What
matters is that the blood that comes out is menstrual blood, regardless of
how long it lasts.

Shaykh Ibn ‘Uthaymeen (may Allah have mercy on him) said:

Shaykh al-Islam [Ibn Taymiyah], Ibn al-Mundhir and a number
of scholars said: It is not correct to set a specific time limit. When a
woman sees the blood that women recognize as menstrual blood, then it is
menses. The evidence for that is as follows:

The general meaning of the verse in which Allah says
(interpretation of the meaning): “They ask you concerning menstruation.
Say: that is an Adha (a harmful thing for a husband to have a sexual
intercourse with his wife while she is having her menses)” [al-Baqarah
2:222]. The words “Say: that is an Adha” imply a ruling connected to the
reason, which is that it is adha. So if this blood, which is the adha, is
seen, and it is not bleeding from a vein, then it is deemed to be menses.
End quote.

Al-Sharh al-Mumti‘, 1/402

And he said:

There are some women who may remain pure (i.e., free of
menses) for four months, then the menses may come and last for an entire
month. It is -- and Allah knows best -- as if it is saved up then comes all
at once. And there are some women who menstruate for three days every month,
or four or five or ten days. End quote.

Al-Sharh al-Mumti‘, 1/402

Based on this, your period is the days on which there is
bleeding, until you see the tuhr (white discharge signalling the end of the
period), even if it lasts for more than fifteen days, so long as the
bleeding does not continue for the entire month or only stops for one or two
days, in which case it is istihaadah (non-menstrual bleeding).

For information on rulings on istihaadah, please see the
answer to question number 68818.